1. Technical Field
The present invention relates to telephones having two or more lines, and more particularly to a circuit that automatically connects a line to a voice circuit in a telephone that does not have an external power source.
2. Background Information
Telephone sets having more than one line for use in a private branch exchange (PBX) system are well-known in the art. A problem with these phones is that mechanical switches are required to select which line is active. The mechanical switches must be physically activated by the phone user, such as by depressing a button to activate line one. The need to physically depress a button to connect a line can cause confusion to a person using the phone. For example, if a switch is set in one position when the telephone is answered, the line indicated by that switch position will be connected to the voice circuit in the telephone, even if the incoming call is on another line. If the person answering the phone does not physically depress the correct line select button, the call will not be connected.
Multiline telephones are also known that have logic capabilities that allow the phone to recognize which line needs to be answered. In these phones, when the user picks up the handset, or presses the speaker phone button, the phone automatically switches to the line having the incoming call. A problem with these phones is that they use a microprocessor to execute the logic functions, and need an external power line to provide the power for the microprocessor. In many situations, such as in hotels and motel industry, running an additional power line to the telephone is very undesirable. Therefore, what is needed is a multiline telephone set having logic capabilities for allowing automatic line selecting functions, but which does not require an external power supply.